THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

ANDERSON COOPER, CNN HOST: I'm Anderson Cooper. This is a CNN special hour "Killings at the Canal: The Army Tapes."

What you're about to see is a story that raises difficult questions about what can happen on a battleground. It's a story about murder in a combat zone. You're going to meet three decorated Army Sergeants, seasoned soldiers, patriotic Americans, who felt they had no other choice but to kill four Iraqis they had taken into custody. They shoot them execution style.

For months, it remained a secret until someone spoke up. On "The Army Tapes," you'll hear military interrogators coax out a reluctant confession of what really happened at the canal.

ABBIE BOUDREAU, CNN NEWS CORRESPONDENT: Anderson, the facts behind the crime are pretty straightforward, but the reason these shootings happened is not. That's what makes the story so complex. The tapes and our investigation reveal these soldiers had a serious problem with the Army's rules on detainees, and why they believe those rules may have pushed them too far.

Here, only on CNN, you'll see exactly what happens in the interrogation room and how the facts would finally emerge.

(BEGIN VIDEOTAPE)

BOUDREAU (voice-over): The wife of an American soldier sits in a grassy field in Germany. This video and the words on her cards are her weapons.

These are the men she's fighting for, three soldiers. Her husband, First Sergeant John Hatley; Sergeant First Class Joseph Mayo; and Sergeant Michael Leahy. Though she still calls them heroes, what they did at this west Baghdad canal would make them killers.

SGT. MICHAEL LEAHY, U.S. ARMY: Put my gun -- I know I shot, but I felt I put my arm like this -- whether I hit him -- I'm not going to say, I didn't hit him because I'm not trying to lie.

UNIDENTIFIED U.S. ARMY OFFICER: You're saying you witnessed people taking those detainees out of it -- someone has to articulate what the hell you're doing parked next to a canal.

LEAHY: I don't think it actually killed him. Whether I would later on, I don't know.

BOUDREAU: We obtained 23 hours of interrogation tapes, tapes you'll only see on CNN. They tell the story of the secret.

UNIDENTIFIED U.S. ARMY OFFICER: On TV they say what happens in Vegas stays in Vegas. Sometimes, sometimes them birds come home to roost from Vegas.

BOUDREAU: The confession.

LEAHY: I'm not a good person because I murdered someone in Iraq.

BOUDREAU: And the fear of it all getting out.

LEAHY: This is going to be -- this is going to be ugly because it is.

BOUDREAU: March 2007, one of the most dangerous times in Iraq, the surge. U.S. soldiers were under constant attack. It was First Sergeant Hatley's third combat deployment. Now 41, he was the trusted leader of Alpha Company 118. He is a veteran of war.

While no one remembers the exact date, no one can forget what happened.

On this particular day, Sergeant First Class Mayo and Sergeant Leahy, both now 28, were helping lead the mission. It started off routine. But it turned into a day that still haunts Private First Class Joshua Hartson.

JOSHUA HARTSON, PRIVATE FIRST CLASS, U.S. ARMY: Clear sky, no clouds. Sun was right on top of everybody.

BOUDREAU: Hartson was 19 when he served under First Sergeant Hatley. That day, he says he remembers receiving small arms fire. His platoon went in search of the shooters. That's when they rolled up on this neighborhood in Baghdad and found four Iraqi men and a small cache of weapons nearby.

BOUDREAU: And did you think these were the men that were firing upon you?

HARTSON: Yes.

BOUDREAU (voice-over): Photos were taken of the four Iraqis. But later destroyed. By all accounts, the men were blindfolded. Their hands zip tied. And they were loaded into the back of a Bradley fighting vehicle.

Sergeant first class Mayo handed Hartson his 9 mm and told him to guard the detainees. (on camera): It was you and them.

HARTSON: Yes.

BOUDREAU: And did any of them speak English?

HARTSON: The one on my right did.

BOUDREAU: So did you try talking to him?

HARTSON: I talked to him.

BOUDREAU: What did you say?

HARTSON: I asked him if he killed Americans, made bombs, and he laughed about the questions.

BOUDREAU: What did that tell you?

HARTSON: Yes, he did. And apparently, it's funny. He enjoys it.

BOUDREAU: According to the Army's rules at the time, the detainees were supposed to be dropped off at the detainee housing area, or the DHA, but that didn't happen. On this day, First Sergeant Hatley had a different plan.

HARTSON: My First Sergeant comes up to me and pulls me away from everybody, then he asks me if we take them to the detainee facility, the DHA, they'll be right back on the streets doing the same thing in a matter of weeks. He asked if I had a problem if we took care of them, and I told them no.

BOUDREAU: What do you think he meant by that?

HARTSON: To kill them.

BOUDREAU: How could you be OK with that?

HARTSON: They were bad guys. If we would have let them go or take them in, we risked the chance of them getting out and killing us, killing other people.

BOUDREAU (voice-over): Hartson remembers one of the Iraqis asking him for a cigarette. The men were still in the Bradley, blindfolded and zip-tied.

HARTSON: Smoke, smoke, smoke. And let them have a couple hits. Then after that, hit hid his hands behind his back. He was holding on to his prayer beads and leaned over and kept saying gift, gift, gift. I said I can't take them. He just kept saying gift, gift, gift again. then I took the prayer beads as a gift.

BOUDREAU: Moments later, the four Iraqis were taken out of the truck and lined up at the edge of a canal in west Baghdad. It was already dark. The three sergeants, Hatley, Mayo and Leahy, pointed their guns at the back of the detainees' heads and, within seconds, executed each of them. Their bodies dumped in the shallow canal never to be found.

HARTSON: Nobody knows what we've all been through, watching people die. And nobody will ever understand it unless they've been there with them.

BOUDREAU: There were a total of 13 soldiers on the mission that day. Some witnessed the crime. Others only heard the shots. Yet, for nine months, all of them kept quiet about what happened at the canal.

But soon that would change.

(on camera): I mean, these men were convicted of premeditated murder.

UNIDENTIFIED SOLDIER'S WIFE: Yes.

BOUDREAU: But you still call them heroes.

UNIDENTIIED SOLDIER'S WIFE: Of course.

BOUDREAU (voice-over): Now new questions about how U.S. soldiers are trained to collect evidence during war and whether the Army's policy drove the soldiers to their breaking point.

(END VIDEOTAPE)

(COMMERCIAL BREAK)

(BEGIN VIDEOTAPE)

JAMIE LEAHY, WIFE OF MICHAEL LEAHY: Yes.

BOUDREAU: Oh, wow. Do you love it?

JAMIE LEAHY: I do. It was the most beautiful thing I had seen and it just looked wonderful on. It's really good to see it again, and -- it's kind of bittersweet, but -- I know it's going to happen.

BOUDREAU (voice-over): Life is on hold for Jamie Leahy.

JAMIE LEAHY: I will wear it. I'm determined to wear it some day with him.

BOUDREAU: They were married by a justice of the peace when her husband was between deployments. But she wanted a traditional wedding, the beautiful gown, the big reception in her grandparents' backyard.

JAMIE LEAHY: This is where the ceremony was going to be. The ceremony over here, with an arch. We were going to have round tables just placed all around.

BOUDREAU (on camera): Did you ever have the ceremony and the reception?

JAMIE LEAHY: No, we haven't yet, because our plans were in February 2008. So -- but -- the investigation started in January. So... BOUDREAU (voice-over): Her husband, Sergeant Michael Leahy, a Purple Heart recipient and a medic, was charged with the unthinkable -- premeditated murder. He was one of three Army sergeants accused in the execution of four Iraqi detainees, and the dumping of their bodies into this canal.

It was a secret he eventually would have to tell his wife. He described that conversation in this Army interrogation tape.

(BEGIN VIDEO CLIP)

MICHAEL LEAHY, ARMY SERGEANT: I told her that, I said, "Honey, I'm going to tell you something and I understand if you don't forgive me, but I'm not a good person because I murdered someone in Iraq. I killed someone in Iraq."

(END VIDEO CLIP)

BOUDREAU (on camera): Did you ever think that your husband was capable of killing like this?

JAMIE: LEAHY: No. I didn't. That's why I -- am trying to understand what was going on in his head. What was going on around him? That could bring him to something, a situation like that.

BOUDREAU (on camera): We've obtained the nearly 900-page investigative case file, as well as 23.5 hours of Army interrogation videotapes, including tapes we asked for, but the Army would not release to CNN.

(voice-over): Those tapes show the agonizing confession of a decorated American soldier, Sergeant Leahy was the only one to confess on tape.

UNIDENIFIED U.S. ARMY OFFICER: When you shot in front of you, where did you shoot?

LEAVY: It was in the back of the head and I guess in the back of the head.

BOUDREAU: Leahy admits he fired two shots but only killed one detainee. So who killed the fourth Iraqi? That was the question Army investigators were trying to answer.

LEAVY: My arm went up to the right and I fired again. I'm pretty sure I didn't hit anybody but I'm not going to say that because I don't know for sure. I wasn't looking when I shot the second round.

BOUDREAU: The interrogator warns him not to lie and presses him for a full confession.

UNIDENTIFIED U.S. ARMY OFFICIAL: But if you did that and you know you did it, because you know whether or not you did it, no reasonable person is going to believe that you shot and those guys fell back on you and then your arm went at this angle. If you shot this dude, just say you shot him. Just be honest about it. LEAHY: It's involved...

(CROSSTALK)

UNIDENTIFIED U.S. ARMY OFFICIAL: I don't know what the guy fell on, but if you purposely shot this guy, Mike, just say it. You've already -- you've already show us what you're made of. I know it's hard. But I know that's what happened, dude. You wouldn't have so much question in your mind right now if you didn't know what happened.

LEAHY: You're right. It is.

UNIDENTIFIED U.S. ARMY OFFICIAL: I know it's hard. Just tell us what happened.

LEAHY: Yes, I turned and shot this guy. but I'm not 100 percent sure I turned and shot this guy.

BOUDREAU: At this point, the Army investigator tries to sympathize with Leahy, a technique commonly used during interrogations and it works.

UNIDENTIFIED U.S. ARMY OFFICIAL: You are not a killer. You are not a [EXPLETIVE DELETED] murder. You acted way out of character and shot somebody, something that you would have never ever done. It's something you'll never do again and you might never have done it without that influence. That's something that extraordinary in your life. It's something that...

LEAHY: I shot the other one.

UNIDENTIFIED U.S. ARMY OFFICIAL: OK.

All right, well, talk to me about what happened, the way you remember.

LEAHY: I shot. The guy did fall. And I did turn. And the other guy was right there in front of me and I shot again. And that guy -- he didn't -- that guy didn't die, by the way. The guy fell down and he was so darn -- I'm not saying crying. He was making noises.

UNIDENTIFIED U.S. ARMY OFFICIAL: Gurgling?

LEAHY: And I hate to point the finger, but I know later...

(CROSSTALK)

... the first sergeant came and shot that guy in the chest. That's the best I know about the situation.

BOUDREAU: Leahy was accusing First Sergeant Hatley of shooting and killing, not just one, but two of the four detainees.

UNIDENTIFIED U.S. ARMY OFFICIAL: After you fired your two shots and you shot them, how did you feel about that incident?

LEAHY: Scared. BDOUREAU: The secret Sergeant Leahy had kept for nine months was now in the hands of Army investigators. He would soon reveal what drove him to murder, and why the Army's policy for detaining prisoners wasn't working.

Jamie Leahy remembers when her husband told her about the investigation.

JAMAIE LEAHY: He was like, are you going to be with me, are you going to stick with me through this? I understand if you don't want to. And then it was kind of like how -- do you feel the same way about me? I told him, I feel the same way about you. I mean, I don't feel any differently, because it's wartime. And it wasn't like he just ran out on the street and shot somebody or something like that.

BOUDREAU: But this former soldier says wartime is no excuse. He's the man who tipped off the government to what happened at the canal, breaking the brotherhood, but at what cost?

CUNNINGHAM, U.S. ARMY: I did the right thing. I'm not going to hide behind the false brotherhood.

UNIDENTIFIED MALE: I would -- if I were Sergeant Cunningham, not be comfortable in a combat environment.

BOUDREAU (on camera): Why do you say that?

UNIDENTIFIED MALE: I'd be worried that having broken the band-of- brothers band, something would happen to me.

(END VIDEO TAPE)

(COMMERCIAL BREAK)

BOUDREAU (voice over): The murders of four Iraqi detainees next to a Baghdad canal remained a secret for nine months and might have stayed that way if it weren't for this man. For the first time, he's talking about why he came forward.

JESS CUNNINGHAM, FMR. ARMY SERGEANT: I feel betrayed. I feel let down. I really feel stabbed in the back.

BOUDREAU: Jess Cunningham is no longer in the Army. The former sergeant is back at home in California. He was at the canal that day in March 2007, but says the murders never should have happened.

(On camera): This is hard for you to talk about.

CUNNINGHAM: I think a lot of soldiers were betrayed. I think the wrong thing was done for someone's ego. And I think that others became followers instead of doing the right thing and taking a good stand and having character and integrity.

BOUDREAU (voice over): Only weeks before the incident, Alpha company lost two soldiers in combat, Staff Sergeant Karl Soto Pinedo and Marieo Guerrero. Cunningham said the losses devastated First Sergeant John Hatley.

CUNNINGHAM: Maybe he did snap. I don't know. Do I think so, no. I believe he knew right from wrong. And I have no respect for him.

BOUDREAU (On camera): You don't have respect for him?

CUNNINGHAM: No. I don't.

BOUDREAU (voice over): Private First Class Joshua Hartson was also at the canal. He feels the decision to kill the Iraqis was the right thing to do. He remembers the night of the murders, First Sergeant Hatley told him the executions were for Soto-Pinedo and Guerrero.

(On camera): It sounds like a revenge killing.

JOSHUA HARTLEY, U.S. ARMY: I don't think it was revenge. It was, these guys were bad. We take them in. They're back out. More weapons they would gather up. More people they might kill. So, we I guess, prevented it by taking their lives.

BOUDREAU (voice over): Hartson and other soldiers like Specialist Jonathan Schafer who is in this Army interrogation video say they kept the murders a secret because their sergeants were like family. Neither was charged in the crime.

I'm friends. I'm family with Sergeant Mayo, First Sergeant, Doc Leahy, I mean, those guys are obviously guys I went downrange with. They're my friend, they're my family. Um, that's why I didn't talk about this, or I decided not to come forward and say, hey, you know, this is what happened down there.

BOUDREAU: But Cunningham did come forward. Nine months after the crime, when he was facing military discipline for assaulting Sergeant Leahy and being disrespectful to another officer, he reported the murders at the canal to his lawyer.

(On camera): You can see why some people might say, well, the only reason you came forward was because you didn't want to get yourself in trouble. You wanted to get out of that situation.

CUNNINGHAM: No, that's not the case. I don't really care what other people think about me. I don't worry. I'm not going to lose any sleep. I did the right thing.

BOUDREAU: Why didn't you report it right away?

CUNNINGHAM: Fear.

BOUDREAU: Fear of what?

CUNNINGHAM: Retaliation, fear of being alone, fear of being the only one that had a problem with it.

BOUDREAU: He says he waited to break his silence until he got back to his military base in Schweinfurt, Germany. He was afraid of reporting the crime while he was in Iraq, fearing his fellow soldiers would turn on him.

DAVID COURT, LAWYER: It was a benefit to have it tried here.

BOUDREAU: David Court is First Sergeant Hatley's attorney, based in Herbz (ph), a small town outside Frankfurt. Court says Cunningham's fears were warranted.

COURT: If I were Sergeant Cunningham, not be comfortable in a combat environment.

BOUDREAU (On camera): Why do you say that?

COURT: I'd be worried that having broken the band of brothers band, something might happen to me.

BOUDREAU: Cunningham says he's not surprised by that comment.

CUNNINGHAM: Exactly why I didn't come forward. But I did the right thing and I'm not going to hide behind excuses. I'm not going to hide behind the false brotherhood.

BOUDREAU: Cunningham and another sergeant were later charged with conspiracy to commit premeditated murder, but those charges were eventually dropped. Based on Cunningham's information, the Army launched a full investigation considering this case "A matter of interest at the highest levels, with the potential for major repercussions."

It was a potential PR nightmare for the Army. This interrogator worried about what would happen when the media found out. He talks to one of the soldiers who was not charged in the case.

UNIDENTIFIED MALE: This is going to be ugly, because it is.

BOUDREAU: He brings up Abu Ghraib, and how the media made that scandal worse than it really was. He feared the same could happen in this case.

UNIDENTIFIED MALE: Just like knuckleheads who were stacking naked prisoners down Abu Ghraib. We walk down the streets and that is a shame that we all carry. And I had nothing to do with that. I don't know about you, but I wasn't at Abu Ghraib. But I can tell you half the time I'm walking down the streets, that's what people think when they're looking at us. Oh, there's those damn Americans that abused those poor prisoners. (EXPLETIVE DELETED) frat boys get abused worse during pledge week in college than that crap. But it's what the media made of it. What the hell do you think they're going to make of this?

BOUDREAU: Investigators questioned all 13 soldiers who were there that day. Most gave permission to be videotaped. Those tapes reveal not only a reason for the murders, but also why soldiers felt the Army's rules protected the enemy more than them; making it increasingly difficult to lock up detainees.

UNIDENTIFIED MALE: Seems like even if you do your job and take these guys to the detainee center, they just coming right back. They're the same (EXPLETIVE DELETED) guys shootin' at you.

BOUDREAU: Why some arguing the Army is simply asking too much.

UNIDENTIFIED MALE: They are asking them to be soldiers and to be cops, but they're just trained to be soldiers.

(COMMERCIAL BREAK)

UNIDENTIFIED MALE: I'm 80 percent sure I shot only two bullets.

BOUDREAU: After hours and hours of interrogations, the Army knew the truth. Three sergeants shot and killed four detainees. Soldiers even sketch the crime scene. It shows the canal and the Iraqis lined up next to it.

First Sergeant John Hatley was the focus of the investigation. Soldiers say it was his idea to kill the men since he believed the rules for holding detainees were not working. He feared the four Iraqis, that his soldiers just captured, would be let go, free to attack another day.

This 2005 memo marked "draft" imposed detailed standards for evidence soldiers needed before suspected insurgents could be detained. "Failure to follow these regulations may result in acquittal or premature release of detainees," according to the document.

Written after the scandal at Abu Ghraib prison and these embarrassing photos were made public. The memo was intended to tighten standards for detaining prisoners.

UNIDENTIFIED MALE: How is everybody doing?

Any kind of problems right now?

BOUDREAU: Brigadier General David Quantock, who now oversees detainees operations, confirms the draft document was operational policy from 2005 through 2008.

BRIG. GEN. DAVID QUANTOCK, U.S. ARMY: Before the memo was written a person could just bring a detainee to our facility and we would take them in, with little or nothing.

BOUDREAU: Soldiers could no longer detain suspected insurgents because they were merely seen as a threat, there now had to be proof. Photographs of physical evidence, photographs of the detainee at the crime scene, and photos of the detainee next to the evidence.

Physical evidence of the crime such as illegal rifles or IED making materials were also needed, along with a sketch of the crime scene, indicating the place of capture and the location of weapons, explosives or munitions. And the most difficult requirement was for statements written by firsthand witnesses to the criminal activity. The new requirements made a soldier's difficult job even more difficult.

(On camera): You've said yourself, General, that there were many military operations where the focus was not on evidence gathering. So what happened in those cases?

QUANTOCK: Well, in most cases, if we don't have anything they eventually are released.

BOUDREAU (voice over): More than 87,000 detainees were captured during the war in Iraq. Quantock says the majority of them, nearly 77,000 were released due to lack of evidence. Despite the high release rate, he says soldiers were perfectly capable of gathering evidence.

QUANTOCK: We're asking them to take basic evidence, which they've been trained to do. Again, we've got the greatest soldiers in the world. And I don't accept that they can't take basic evidence off of -- off of a crime scene.

BOUDREAU (on camera): General, though, if it's so easy to collect this basic type of evidence then why were so many detainees let out because of lack of evidence?

QUANTOCK: Well, I mean, it took us a while. I mean it took us a while to realize. It goes back to my point about, you know, we were -- we're trying to make the fight fit the Army as opposed to have the Army fit the fight. I think a lot of times we thought the insurgency would dissipate. We were working closely with the government of Iraq. We were trying to improve the Iraqi security forces, but at the end of the day it didn't work out very well. We had to get better at taking evidence off the crime scene.

FRANK SPINNER, LEAHY'S ATTORNEY: They're asking them to be soldiers and to be cops but they're just trained to be soldiers.

BOUDREAU (voice over): We met Sergeant Leahy's attorney Frank Spinner in Colorado Springs. His work defending accused war criminals takes him all over the world.

SPINNER: As it was, they had to take off their soldier helmet, put on their cop hat, take them to a civilian sort of police station, and show evidence that these were people that were shooting at them. And if there wasn't enough evidence then they were going to be released on the street.

And -- but soldiers aren't trained to be cops. And they're not trained to collect evidence and they're to the trained in the ways of civilian criminal prosecutions.

BOUDREAU: A point even General Quantock concedes when pressed.

(On camera): You've talked quite a bit about the training that soldiers have received. We've talked to many, many soldiers who say that the only kind of training that they would get would be, you know, a 15-minute Power Point presentation back in the States, before they would go out on a battlefield.

QUANTOCK: Yeah, that's exactly right. I mean, we don't give them extensive training. We're not trying to teach policemen, but we are trying to teach them enough whether it's eyewitness statements, whether it's taking photograph, all of those can be used in a trial. However, we got to catch somebody doing something wrong. We've got to find evidence.

BOUDREAU (voice over): According to General Quantock, the 20050 rues were meant to kept possible insurgents locked up and secure a criminal conviction in the Iraqi court system. But on the tapes of the Army investigation into the killings of the four Iraqi men, the U.S. soldiers made it clear it wasn't working that way.

UNIDENTIFIED MALE: It seems like even if you do your job and take these guys to the detainee center, they come right back. The same guys (EXPLETIVE DELETED) shooting at you.

BOUDREAU: And in the field, the rules could be even stricter. In this document obtained by CNN, an Army intelligence officer attached to Alpha Company said, "statements from U.S. service members were not accepted as proof of insurgent activity." And that the detention facility "required at least two witness statements from Iraqis."

General Quantock told us Iraqi witnesses were preferred, but not required.

(On camera): With all due respect, General, what is the point of having soldiers in Iraq fighting this type of war, if they can't take alleged insurgents off the street?

QUANTOCK: Well, we've -- we've -- as we look at Iraq we look at Iraq as a long-term strategic partner of the United States. The sacrifice is well worth it. What we're trying to do is build capacity, and capability for not only the Iraqi force, the police, the Iraqi army, but also stand up the rule of law.

BOUDREAU: The rules got even tougher this year. A security agreement with the government of Iraq now requires an arrest warrant, signed by an Iraqi judge to detain someone. Michael Waddington represents Joseph Mayo, one of the three sergeants who shot a detainee.

(On camera): Would you be surprised if other soldiers have done the same thing that these three soldiers did when they pulled the trigger?

MICHAEL WADDINGTON, MAYO'S ATTORNEY: No, that wouldn't surprise me at all. Soldiers will do what they have to do to stay alive, following the law, but if the law and rules don't protect them, then soldiers will have to do to make sure they come back alive and their buddies come back alive.

BOUDREAU: But do the frustration over these new standards of evidence lead to murder?

(On camera): Did your husband reach his breaking point?

QUANTOCK: There's never an excuse to execute anyone. They become judge, jury and executioner.

(COMMERCIAL BREAK) BOUDREAU: With four Iraqis murdered and three U.S. soldiers blamed, including First Sergeant John Hatley, his wife, Kim, felt she had to do something. She came up with a video and these handwritten cards. In this field near her home in Schweinfurt, Germany, where her husband was based, she silently told her story.

(On camera): She very simply just wrote words on these cards to express what happened; and how she was feeling. This one is interesting, "To free these three American heroes."

I mean, these men were convicted of premeditated murder.

KIM HATLEY, WIFE OF SGT. JOHN HATLEY: Yes.

BOUDREAU: But you still call them heroes?

HATLEY: Of course. They served their country. And they've been through a lot and so have the family members, but in life, with any challenge, you can't just look at one incident. That does not define who these soldiers are.

BOUDREAU: Kim's husband was accused of coming up with the plan to kill the detainees.

UNIDENTIFIED MALE: The decision was made. We are going to take these (EXLETIVE DELETED) out and give them lead poisoning and be done with it.

BOUDREAU: On this Army interrogation tape the investigator tells Hatley he already knows what happened at the canal.

UNIDENTIFIED MALE: Good concept, good concept, bad execution. And, you know, I'd like to make this right. Because if not, we are going to have a couple of dozen (EXPLETIVE DELETED) up Joes, we are going to have a smeared unit lineage, and we are probably going to have a smeared United States Army and United States of America over this.

BOUDREAU: The investigator informed Hatley the secret is out, and it's bond to get worse.

UNIDENTIFIED MALE: We got a hell of a lot of pretty damn concerned high-level people way above my pay grade, that are grabbing their ankles and bracing for be an ugly damn mess if this becomes a big drawn out public knife fight.

BOUDREAU: Hatley would eventually ask for a lawyer and that would end this session. He left no clues as to why he pulled the trigger that day.

This video was shot during Hatley's four day trial. You can barely make them out, but that is John and Kim Hatley walking into court.

UNIDENTIFIED MALE: Go away for respect for them.

BOUDREAU: Soldiers shield him from our camera. They form a barricade, once again, protecting their leader. All three soldiers were convicted of premeditated murder and conspiracy to commit premeditated murder. In this military courtroom in Vilseck, Germany. They are now all prisoners at Fort Leavenworth, in Kansas.

Two other soldiers were sent to prison but are now free. Joshua Hartson is the private who confronted our camera crew. He was one of the last soldiers to see the four detainees alive. He says First Sergeant Hatley was a father figure. And to this day he feels the right decision was made at the canal.

(On camera): This was premeditated murder. When you hear those words and you know that you had a role, what are you thinking?

JOSHUA HARTSON, FMR. PRIVATE FIRST CLASS: Why am I not in prison with them?

BOUDREAU: Should you be?

HARTSON: I would love to say no, but, yeah.

BOUDREAU: Hartson, along with most of the other soldiers at the canal, were disciplined by the Army and received immunity for their testimony. Hartson left the Army after a serious injury. Kim Hatley says she doesn't believe any of the soldiers should be in prison.

(On camera): Did your husband reach his breaking point?

HATLEY: That's a possibility.

BOUDREAU: Do you think he did?

HATLEY: I'm not sure. I'm not sure. I know that he was tired. He actually told me that he was tired multiple times. There's quite a few medals on there.

BOUDREAU: Kim says her husband never told her why her husband came up with the idea to kill the four detainees. But these documents may provide some insight. They summarize an interview with an intelligence officer attached to Alpha Company.

The intelligence officer states Hatley and his soldiers once captured a suspected bombmaker, they found electronic parts used to make explosives at his house. But the detainee claimed he was an electronics repairman and was let go. Hatley and the other soldiers were then forced to bring him back to his house, quote, "Giving him a letter of apology and a fistful of cash for his troubles."

The intelligence officer states, in his opinion, even a reasonable person will, quote, "do what they need to do to ensure the survival of the unit." We asked Brigadier General David Quantock about the detainee policy in light of the killings at the canal.

(On camera): Do you think the policy is so flawed that something like this could happen?

QUANTOCK: Well, there are the rules of war, and those soldiers knew those. There is never an excuse to execute anyone. They become judge, jury and executioner. That is not the way we do things in the United States. That is not the way we were trained. That is not the way we do things in our Army.

BOUDREAU: But the wives of these soldiers say the Army let them down.

JOHANA MAYO, JOSEPH MAYO'S WIFE: He has been punished enough. He definitely wants to get out of there. He doesn't think he belongs there, either. Doesn't deserve to be there.

BOUDREAU: In a moment, from inside the concrete walls at Fort Leavenworth, finally First Sergeant Hatley's side of the story.

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BOUDREAU (voice over): Johanna Mayo doesn't feel her husband, Sergeant First Class Joseph Mayo, betrayed anyone when he shot one of the Iraqis in the back of the head next to a Baghdad canal.

MAYO: I knew he was on trial for murdering the Iraqi detainees that they had captured.

BOUDREAU (On camera): It was hard for you to say the word "murder".

MAO: Yeah. That's not the word I want to use. I just can't think of --

BOUDREAU: You don't look at your husband like a murderer?

MAYO: No, not at all.

BOUDREAU: She says her husband is a good soldier. He was awarded the Purple Heart after an IED exploded, resulting in a brain injury. His doctor told her he still suffers from post traumatic stress disorder and memory loss. It was his third combat deployment.

MAYO: I think that he's given a sacrifice a lot. I think he's -- he's a war hero. He's not a criminal.

BOUDREAU: The Mayos have been married for nine years, they have three children. The oldest is 11 years old.

MAYO: Who's that?

UNIDENTIFIED FEMALE: Da.

MAYO: Da-da?

BOUDREAU: Their youngest is only 15 months. Then there's six-year- old Joseph. Just from watching him play you can't tell there is anything wrong. But he suffers from congenital scoliosis that will soon require surgery. And Johana Mayo, legally blind, cannot drive. She can barely make out her husband's letters.

(On camera): How are you doing? I miss you guys so much. I'm doing good, just thinking about three all the time. MAYO: He was the one that drove the kids around. He was one that took care of their homework and anything, grocery shopping, everything. I relied on him for everything. And now, I feel like I have to turn to my daughter a lot and she's only 11.

BOUDREAU (voice over): The incident at the canal that day changed this family.

(On camera): Are you angry, at all, at your husband for him making that decision?

MAYO: No, not at all. Knowing how my husband felt about those soldiers, about those soldiers were his family. And knowing that what he did was to protect his family it -- it doesn't make me angry at all.

BOUDREAU (voice over): These military wives are used to their husbands not being home, but this, they say, is different. Once decorated heroes their husbands are now convicted war criminals. Sergeant First Class Mayo pleaded guilty to the murder charges. The other two sergeants were convicted at trial.

Kim Hatley, the wife of First Sergeant John Hatley, says she refuses to let herself cry, even in private because she needs to be strong for her husband and her 19-year-old son, who is now fighting in Afghanistan.

(On camera): Some people might call your husband a murder.

HATLEY: Mm-hmm.

BOUDREAU: What do you call him?

HATLEY: I call him a good man.

BOUDREAU: She has no reason to stay in Germany any longer. She's packing up her life and moving to Texas. Her husband's home state.

JAMIE LEAHY, WIFE OF MICHAEL LEAHY: OK. Here's the card for you, too.

UNIDENTIFIED FEMALE: Oh, thanks.

BOUDREAU: Jamie Leahy, the wife of Mike Leahy, works at her mom's beauty salon. It was never part of the plan but keeps her mind occupied.

(On camera): Is it upsetting when people hear about what happened in your husband's case and they look at him and they think, monster.

LEAHY: It does. Because it makes me feel like you don't know who you are talking about at all. He is a person. He's a son. He's my husband.

BOUDREAU: And Johana Mayo, the wife of Sergeant First Class Joseph Mayo, struggles to hold her family together. (On camera): Do you believe you'll get through this?

MAYO: Yes. I know we will. It's just -- it's just, you know, it's hard right now but we'll get through it.

BOUDREAU: Three wives now waging a battle of their own. They want their husbands home, but they have a long wait.

CNN requested interviews with each of the three soldiers but Army policy prohibits media interviews with prisoners, yet this man was given rare access. We met up with him outside the gates of Fort Leavenworth, moments after he spoke with two of the soldiers.

Stjepan Mestrovic is a sociology professor and has written books about war crimes. He also consulted with the defense on the Leahy and Mayo cases, which allows him inside the prison.

STJEPAN MESTROVIC, SOCIOLOGY PROFESSOR: I mean, they are afraid that people look at them and say, you know, monsters. I know they are not. They have no prior records. They love their families. What Michael Leahy told me was, very bluntly, he said, you know, if they let me out tomorrow, I would never go out and do any crime. I never did before. What people don't understand is, we are different people over there. It's Iraq.

BOUDREAU: Mestrovic says both Mayo and Leahy have lost weight and have a hard time sleeping.

(On camera): Do you think from your conversation with them that they care about what Americans think about them?

MESTROVIC: They care a lot, yes. You have to remember in their minds they are patriotic. In fact, one of them said to me, they feel the Army misused their patriotism. They feel betrayed by the Army.

BOUDREAU: Mestrovic did not meet with Hatley, but now we hear from him for the first time from inside Fort Leavenworth.

Hatley explains the difficulties of evidence collection in a war zone, in this letter to CNN. He writes, quote, "The guidelines established for detaining and prosecuting the enemy has extensive flaws."

Hatley says he would capture the enemy, but then be forced to release them "two to three days later," because of lack of evidence, or because the "weapons or explosives found on the individuals were not found in the same portion of the house that the insurgents were found in."

He says he repeatedly found himself, "fighting the same enemy again and again.

"I assure you," he writes, "the military spared no expense in the prosecution of my soldiers and me. If they would have spent half the time, effort, and money in prosecuting the enemy as they had in prosecuting us, I assure you we would have never found ourselves in our current situation." (On camera): Lawyers say it could take years for the appeals process to be completed but the one outstanding question, of course, is for soldiers on the battlefield, could this happen again.

COOPER: Abbie, thanks very much. Thanks for watching the CNN Special Investigations Unit, our "Killings at the Canal: The Army Tapes."